Basic Unit Testing with Mockito
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This document discusses different approaches to unit testing with mocks using Mockito. It explains that mocks allow isolating dependencies to test units in isolation. It compares directly mocking dependencies with Mockito's mocking features like stubbing, argument matchers, custom argument matchers, argument capture, and verification. Mockito provides cleaner mocking by separating stubbing from verification and supporting flexible argument matching.
Basic Unit Testing with Mockito
- 1. unit testing on the rocks!
- 2. Why mock?
- 3. Isolation
- 4. Example AccountController HellotxtManagement +addAccount +deleteAccount ... ...
- 5. Example AccountController HellotxtManagement +addAccount +deleteAccount ... ...
- 6. The no-so-good way HellotxtManagement ... HellotxtManagementMock void addAccount(){ //do what I want } ..
- 7. The no-so-good way HellotxtManagement ... HellotxtManagementMock HellotxtManagementMock2 void addAccount(){ void addAccount(){ //do what I want //now do this } } .. ..
- 8. The no-so-good way HellotxtManagement ... HellotxtManagementMock HellotxtManagementMock2 HellotxtManagementMock3 void addAccount(){ void addAccount(){ void addAccount(){ //do what I want //now do this //throw exception } } } .. .. ..
- 10. The mockito way
- 11. Test Workflow 1. Create Mock 2. Stub 3. Invoke 4. Verify 5. Assert expectations
- 12. Creating a Mock import static org.mockito.Mockito.*; ... // You can mock concrete classes, not only interfaces LinkedList mockedList = mock(LinkedList.class);
- 14. What’s going on? // following prints "first" System.out.println(mockedList.get(0)); // following throws runtime exception System.out.println(mockedList.get(1)); // following prints "null" because get(999) was not stubbed System.out.println(mockedList.get(999));
- 15. Verify // Although it is possible to verify a stubbed invocation, usually it's // just redundant // If your code cares what get(0) returns then something else breaks // (often before even verify() gets executed). // If your code doesn't care what get(0) returns then it should not be // stubbed. Not convinced? See here. verify(mockedList).get(0);
- 16. What about void methods? • Often void methods you just verify them. //create my mock and inject it to my unit under test DB mockedDb = mock(DB.class); MyThing unitUnderTest = new MyThing(mockedDb); //invoke what we want to test unitUnderTest.doSothing(); //verify we didn't forget to save my stuff. verify(mockedDb).save();
- 17. What about void methods? • Although you can also Stub them to throw an exception. @Test(expected = HorribleException.class) public void test3() throws Exception { // create my mock and inject it to my unit under test Oracle oracleMock = mock(Oracle.class); MyThing unitUnderTest = new MyThing(oracleMock); String paradox = "This statement is false"; // stub doThrow(new HorribleException()).when(oracleMock).thinkAbout(paradox); unitUnderTest.askTheOracle(paradox); }
- 18. Argument Matchers when(hellotxtManagementMock.addAccount(Mockito.any(Session.class), Mockito.anyString(), Mockito.anyMap(), Mockito.anyString())).thenReturn(account);
- 19. Custom Argument Matcher Mockito.when(hellotxtManagementMock.getAuthenticationInfo(Mockito.argThat(new IsValidSession()), Mockito.eq(Networks.FACEBOOK))).thenReturn(expectedResult); ... private class IsValidSession extends ArgumentMatcher<Session> { @Override public boolean matches(Object argument) { return argument instanceof Session && ((Session) argument).getSessionId().equals(TestValues.VALID_SESSION_ID); } }
- 20. Argument Capture ArgumentCaptor<Session> sessionCaptor = ArgumentCaptor.forClass(Session.class); ... ModelAndView result = accountController.addAccount(json.toString(), sessionId, deviceType, deviceId, networkId); ... verify(hellotxtManagementMock).addAccount(sessionCaptor.capture(), Mockito.eq(networkId), Mockito.eq(parameters), Mockito.eq(redirectUrl)); ... assertEquals(sessionId, sessionCaptor.getValue().getSessionId()); assertEquals(deviceType, sessionCaptor.getValue().getDevice().getType().name()); assertEquals(deviceId, sessionCaptor.getValue().getDevice().getUid());